This invention relates to sorbent systems and, more particularly, to sorbent systems for removal of water from air.
Conventional sorbents, such as zeolitic molecular sieves, silica gel, or clay, are commonly known and used for removal of water and/or carbon dioxide from air. Although effective, these conventional types of sorbents have several drawbacks that limit widespread use. For example, conventional sorbents strongly bind the adsorbed water, which may make regeneration difficult or too inefficient to be practical. For example, the binding energy (i.e., heat of adsorption) of water is about 1800 btu/lb for a zeolite and 1300 btu/lb for silica gel. After reaching full adsorption capacity, the sorbent may be heated in a regeneration step at a relatively high temperature, such as 150° C. (302° F.) to 190° C. (374° F.), to overcome the binding energy and recover a portion of the adsorption capacity. Because of the elevated binding energies, complete desorption of the adsorbed water may not occur. The sorbent may then be less effective in subsequent adsorbing cycles because of residual adsorbed water. Alternatively, the sorbent may be discarded and replaced with new sorbent. Thus, conventional sorbents may require significant heat energy or replacement expenses.
Accordingly, a sorbent system that provides water removal and relatively low regeneration temperatures is needed. This invention addresses those needs while avoiding the shortcomings and drawbacks of the prior art.